The way this bug works, is when another mob is created while in a container, such as locker it will be inside the locker with the original source.
Now put that source in a single player content unit, a sleeper, for example.
When the Alien bursts from the Marine it's put into the Sleeper with the Marine, but ejecting the Sleeper will only pull out the source mob, the Marine. Afterwards, the Alien will technically still be -in- the sleeper, unable to escape. If they were to evolve and melt the pod, then they would cause the Sleeper to be deleted, which deletes all Content, this contents being, the alien.
Steps to reproduce:
1. Infect a Marine
2. Put Marine in Sleeper (Or Advance Scanner or Cryo or Cryostasis Pod)
3. Hatch!
To get out.
4. Spit or Delete the Sleeper
5. Be Deleted.
